| Company / developer | International Computers and Tabulators |
|---|---|
| Programmed in | Assembler |
| Working state | Historic |
| Source model | Source available to licensees. |
| Initial release | 1960s |
| Latest stable release | 8,67 / 1985 |
| Available language(s) | English |
| Supported platforms | ICT 1900 series of computers |
| Kernel type | Monolithic |
| Default user interface | Command line (teletype or block mode terminal) |
| License | Proprietary |
GEORGE was the name given to a series of operating systems released by International Computers and Tabulators (ICT) in the 1960s, for the ICT 1900 series of computers.
Initially the 1900 series machines, like the Ferranti-Packard 6000 on which they were based, ran a simple operating system known as executive which allowed the system operator to load and run programs from a Teletype Model 33 ASR based system console.
In December 1964 ICT set up an Operating Systems Branch to develop a new operating system for the 1906/7. The branch was initially staffed with people being released by the end of work on the OMP operating system for the Ferranti Orion. The initial design of the new system, named George after George E. Felton, head of the Basic Programming Division, was based on ideas from the Orion and the spooling system of the Atlas computer. [1]
(In public it was claimed that George stood for GEneral ORGanisational Environment, but contemporary sources say that was a backronym).[2]
In July 1965 a team from ICT was present at a seminar at NPL describing the CTSS operating system developed for MITs Project MAC. They decided that the ICT would need to provide multi-access facilities, known to ICT as MOP, "Multiple Online Processing". In November 1965 H. P. Goodman, head of the Operating Systems Branch attended the Fall Joint Computer Conference in Las Vegas where plans for Multics were initially described.[3] Some of the Multics features discussed influenced future development of George, notably the tree structured filestore.
Towards the end of 1965 ICT marketing requested that a simpler operating system be made available quickly, especially for the smaller members of the range. It was decided that two smaller systems, known as George 1 and George 2 be released rapidly, and the larger operating system was renamed George 3.
Contents |
George 1 was a simple batch processing system, Job descriptions were read from cards or paper tape which controlled the loading and running of programs, either loaded from cards or paper tape or magnetic tape. The job control language allowed definition of the peripherals and files to be used and handling of exception conditions. The job description would be checked for errors before the job was run. George used the trusted program facilities provided by executive to run the user programs.
George 2 added the concept of off line peripheral handling (spooling). Several different modules, running in parallel, allowed overlapping of input, processing and output operations:
If the installation was large enough multiple copies of the central module could be run, allowing multiple jobs to be processed in parallel.
The George 2 job control language allowed use of stored macros with conditional facilities.
George 2 provided no file system, the system and user programs relied on the facilities provided by executive. Files on disk were accessed by unique 12 character names and no security other than a "do not erase" bit was provided.
MINIMOP could be run simultaneously with GEORGE 2 on the same machine, to provide on-line time-sharing facilities.
Here is a, somewhat artificial, example batch for George 2:
JOB PLAN4JOB,30174,BRIAN
IN ED(PROGRAM COMP) LOAD #XPLT IN CR0(SOURCE) ENTER 1
AT HALTED OK,GO TO 1A DISPLAY 'COMPILATION ERRORS' GO TO 5END
1A IN ED(PROGRAM COMP) LOAD #XPCK IN CR0/JD *IN ED(SEMICOMPILED) *OUT ED(PROGRAM TEST) *LIST ???* ENTER 1 AT DELETED HH,GO TO 2A DISPLAY 'CONSOLIDATION ERRORS' GO TO 5END
2A IN ED(PROGRAM TEST) LOAD #HWLD ENTER 0 5END END ****
DOC SOURCE
PROG(HWLD)
STEER(LIST,OBJECT)
OUTE(SEMICOMPILED(0))
WSF(HWLD)
PLAN(CR)
#PRO HWLD40/TEST
#LOW
MESS 12HHELLO WORLD
#PRO
#ENT 0
DISTY '11/MESS'
DEL 2HOK
#END
ENDPROG
****
END BATCH
In a real application the job would probably use a stored macro and be much simpler, this example has been written out longhand in an effort to show some of the features of the JCL.
GEORGE 3[4] was the main version of the operating system series for the larger machines of the 1900 series. Initially it was released for the 1906/7, eventually it was made available for models down to the 1902T. In contrast to George 1&2 which ran as user mode programs under executive George 3 was a full operating system, leaving only low-level peripheral and interrupt handling to a cut-down version of executive.
George 3 was implemented as a small memory resident part and a collection of chapters (overlays) which were loaded into and removed from memory as needed. Chapters were strictly location independent, allowing best use of memory. Internally George used cooperative multitasking, context switches could take place at any chapter change (call from one chapter to another), or at other specified places in the code. User level code was run using preemptive multitasking, context switches were forced on I/O operations or clock ticks.[5]
George was written in a special assembler, GIN (George INput), which had richer conditional compilation and macro facilities than the standard PLAN assembler. Macros were heavily used by the code to reduce the effort of programming such a large system in assembly language. In later versions the macro features of GIN were used to add structured programming features to the code. Writing the system was estimated to have taken 75 programmer-years of effort.[6]
George 3 was a mixed batch and online system. Jobs could be run from cards or tape in the same manner as George 2, or interactively from MOP (Multiple Online Processing) terminals, either simple Teletype Model 33 ASR terminals or block mode VDU terminals.
The job control language was the same on terminals or in batch jobs and included conditional operations and macro operations. In contrast to Unix systems the job control language was part of the operating system rather than being a user level shell process.
A job could only have one program loaded in to memory at a time, but one job could start other jobs to run concurrently, if system resources and site policy would permit. The system would swap user programs out of memory while they were waiting for input or output if other activities required memory to run.
George 3 provided a tree structured file store, inspired in part by Multics.
Every user of the system had a home directory with as many sub directories as needed under it. A users home directory could be accessed directly, for example the directory for user JOHN could be referred to as :JOHN, or by a full path, for example if JOHN was in the computer science department his home directory might be :MASTER.USERS.COMPSCI,JOHN.
Access control lists were used for security, a user could permit or deny any user or group of users access to his files or directories.
The file store was two-level, files could be either currently on disk, or, if the system was low on disk space they would be archived to tape. If an attempt was made to access a currently off line file the job would be suspended and the operators requested to load the appropriate tape. When the tape was made available the file would be reloaded and the job resumed.
Starting with the 1904A, a paging unit was available for larger 1900 processors and George 4 was written to take advantage of it. George 4 remained compatible with George 3. (It was common to alternate George 3 and 4 on the same machine and filestore, running George 3 during the day for small, interactive workloads and George 4 at night for large, memory intensive, jobs.)
George 4 introduced the concept of a sparse program, a program that had an addressing space larger than its allocated memory and read-only (pure) data and code regions. New versions of the consolidator (linker) and compilers were provided to use these facilities.
The source code of George 3 and 4 were the same; conditional compilation facilities of the GIN assembler were used to select which version of the system was being compiled.
As the 1900 paging feature was not emulated by the 2900 series machines used by later George installations, George 4 fell out of use before George 3.
Here are some simple examples of George use
The job is modelled on the George 2 job above, and like that job is somewhat artificial as in real use most of the work would be done by a pre-stored macro command.
The job would be read in from a card or paper tape reader. With minor changes (removal of the first "JB" command) it could be stored in a file and run from an interactive (MOP) terminal.
JB PLAN4JOB,:BRIAN,T####
WE COMERR,GO 5CE MZ 20K
CE !
IN !,T////
PROG(HWLD)
STEER(LIST,OBJECT)
OUTE(SEMICOMPILED(0))
WSF(HWLD)
PLAN(CR)
#PRO HWLD40/TEST
#LOW
MESS 12HHELLO WORLD
#PRO
#ENT 0
DISTY '11/MESS'
DEL 2HOK
#END
ENDPROG
////
LO :LIB.PROGRAM XPLT RM IF NOT HAL(LD),GO 1F
AS *CR0,! ER !
CE ! AS *LP0,!
CE !(*DA,BUCK1,KWOR40) AS *DA2,!(WRITE)
EN 1 IF HAL(OK),GO 1A 1F DP 0,COMPILATION ERRORS GO 5EX
1A DL
CE ! IN !,T//// *IN ED(SEMICOMPILED) *OUT ED(PROGRAM TEST) *LIST ////
LO :LIB.PROGRAM XPCK RM IF NOT HAL(LD),GO 2F
AS *CR0,! ER !
AS *LP0,!1(APPEND) LF !1,*LP,PA ER !1 AS *DA1,! ER ! CE !(*DA,BUCK1,KWOR10) AS *DA13,!(WRITE) ER !
CE PROGRAM HWLD(*DA,BUCK1,KWOR5) AS *DA14,PROGRAM HWLD(WRITE) EN 1 IF DEL(HH),GO 2A 2F DP 0,CONSOLIDATION ERRORS GO 5EX
2A LO PROGRAM HWLD EN 0 DP 0,JOB COMPLETED GO 5EX
5CE DP 0,COMMAND ERROR IN JOB
5EX IF COR,DL EJ ALL
####
All user input is shown in lower case. All output from George is in upper case.
THIS IS GEORGE 3 MARK 8.67 ON 21MAR11 21.21.23← ln :john,mopjob TYPE PASSWORD← password STARTED :JOHN,MOPJOB,21MAR11 , 21.21.35 TYPE:MOP
21.21.35← mk hellodir 21.28.10← dy hellodir
21.28.16← newcopyin (123457) 21.28.32 JOB IS NOW FULLY STARTED 21.28.32 0.03 CORE GIVEN 4736 WAITING FOR MT 123457
ERROR IN PARAMETER 2 IN OL IN NEWCOPYIN: MT (123457) CORRECTLY IDENTIFI ED BUT NOT AVAILABLE DISPLAY: ERROR IN NEWCOPYIN . MACRO ABANDONED 21.28.58 FREE *CR0 ,0 TRANSFERS 21.28.58 0.05 DELETED,CLOCKED 0.00 0.05 :DELETED END OF MACRO
21.28.58← newcopyin (123456) 21.32.21 0.06 CORE GIVEN 4736 WAITING FOR MT 123456 21.32.34 USED U31 AS *MT0 , MT (123456,HELLOTAPE(0/0)) ← hello,hello(/plan) ← **** 21.32.52 FREE *CR0 ,2 TRANSFERS DISPLAY : 1 PARAMETER ACCEPTED DISPLAY 0.08: MONITOR DISPLAY : INPUT TAPE * 123456. DISPLAY 0.08: MONITOR 21.32.52 FREE *FH0 ,1 TRANSFERS 21.32.52 FREE U31,8 TRANSFERS 0.10 :DELETED : OK 21.32.52 0.10 DELETED,CLOCKED 0.00 END OF MACRO
21.32.52← lf hello
#PRO HWLD40/TEST
#LOW
MESS 12HHELLO WRLD
#PRO
#ENT 0
DISTY '11/MESS'
DEL 2HOK
#END
21.33.01← ed hello EDITOR IS READY 0.0← tc/wrld/ 2.0← r/wrld/world/ 2.29← e
21.43.46← plancomp *cr hello(/plan),*idhelo FILES ALREADY ONLINE: :LIB.SUBGROUPS-RS(1/V3) :LIB.PROGRAM XPCK(1/V12K) :LIB.PROGRAM XPLT(1/V8C) 21.43.58 0.58 CORE GIVEN 18944 0.58 :HALTED : LD DISPLAY : START JOB HELO, OPEN *DA2 N CA 1641 M=#00100 FN=SEMICOMPILED 1.00: MONITOR 21.43.58 FREE *CR0 ,8 TRANSFERS DISPLAY : COMP OK 84 #HELO 21.43.58 FREE *DA2 ,9 TRANSFERS 1.01 :DELETED : FI #XPCK 21.43.58 FREE *TR0 ,7 TRANSFERS 21.43.58 FREE *LP0 ,83 TRANSFERS 21.43.58 1.01 DELETED,CLOCKED 0.00 21.43.59 1.07 CORE GIVEN 11392 21.43.59 FREE *CR0 ,5 TRANSFERS 21.43.59 FREE *DA14,20 TRANSFERS 21.43.59 FREE *DA1 ,9 TRANSFERS 21.43.59 FREE *DA2 ,2 TRANSFERS 21.43.59 FREE *DA13,7 TRANSFERS 1.07 :DELETED : HH 21.43.59 FREE *LP0 ,32 TRANSFERS 21.43.59 FREE *DA15,0 TRANSFERS 21.43.59 1.07 DELETED,CLOCKED 0.00 DISPLAY: PLAN COMPILATION/CONSOLIDATION OKAY END OF MACRO
21.43.59← lo program helo 21.44.06← en 21.44.07 1.09 CORE GIVEN 64 DISPLAY : HELLO WORLD 1.09 :DELETED : OK 21.44.07 1.09 DELETED,CLOCKED 0.00
21.44.07← lt MAXIMUM ONLINE BS USED 252 KWORDS 21.44.12 1.09 FINISHED : 0 LISTFILES BUDGET USED LEFT TIME(M) 70 -97797 MONEY 35 80327 21.44.12←
George was distributed in a form that allowed a site to modify large parts of the system. A compilation of the system was started, then interrupted just before the end and dumped to magnetic tape. The GIN compiler allowed the compilation to be continued from this point at the user site, possibly modifying code already compiled.
Versions of George 3 before release 8 were provided in binary form. Any modifications needed to the system were made as binary patches. To simplify the process most George chapters included an empty MEND area at the end.
Starting with release 8 the source of George was distributed with the binary, both on magnetic tape and microfiche. A system of source level patches, known as MENDITS was used to modify the system and an existing chapter could be completely replaced by the new modified chapter.
The George user group set up a "MEND exchange scheme" to share interesting modifications to George. Some modifications were distributed freely, others were available for a fee. When ICL produced a new version of George they would sometimes include modifications produced by the users.
For the last released version, 8.67, most of the patches from the MEND exchange scheme were included in the standard George source, switched off by conditional compilation. They can be turned on as part of the standard process of tailoring George for a site.
With the release of ICL's "new range", the 2900 series with its VME operating system George became obsolete. However, due to the legacy of investment in software for George, ICL released options to run 1900 series software, including George, on 2900 series machines, initially the Direct Machine Environment (DME), later the Concurrent Machine Environment (CME) which allowed simultaneous running of 1900 and 2900 code on the same system.
New versions of George 3 continued to be released for the 2900. The last version was 8.67, released in 1983.
As of 2005 at least one site in Russia was still running George 3 under DME.[7]
David Holdsworth and Delwyn Holroyd obtained copies of George 3 issue tapes when the last live site in the UK, at British Steel, was being decommissioned and wrote an emulator for the 1900 hardware and executive that allows running of George on Microsoft Windows as part of a project for the Computer Conservation Society.
Tests with the emulator show that George 3 is Y2K compliant.